US5374933A
Expired / Lapsed
US
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Position correction method for vehicle navigation system
Assignee: TomTom International BV
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Filing: 1993-01-05
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Granted: 1994-12-20
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Expires: 2013-01-05
Abstract
Abstract A vehicle navigation system is used to determine the absolute position of a vehicle with improved accuracy on freeways or rural highways. First, the system stores a known vehicle position in its memory. As the vehicle moves away from the known position, the system uses a variety of means to sense external signals. These means include satellite transmission receivers and magnetic compasses. When a change in the external signals occurs, the system recognizes the presence of a landmark which can then be used to set the vehicle's position. To accomplish this, the system's data processor searches a map data base, attempting to fix the position of the sensed landmark with respect to the initially stored known position. When the system identifies the most likely landmark, the position of the vehicle is then reset to that position.
Inventors
- 👤 Wei-Wen Kao
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 22:05
CPC Classifications
H; H04; H04B; H04B7/00; H04B7/14; H04B7/15; H04B7/185; G; G01; G01C; G01C21/00; G01C21/26; G01C21/28; G01C21/30; G01S; G01S19/00; G01S19/01; G01S19/13; G01S19/24; G01S19/38; G01S19/39; G01S19/40; G01S19/26
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
91 words
A method for determining a current vehicle position in a vehicle navigation system having a map data base, the method comprising the steps of: storing a first vehicle position; moving the vehicle from the first vehicle position; sensing an external signal while moving the vehicle; detecting a change in the external signal caused by the presence of a landmark; examining the map data base to find a most likely landmark position corresponding to the change in the external signal; and updating the current vehicle position to the most likely landmark position.
Claim 2
Independent Claim
91 words
A method for determining a current vehicle position in a vehicle navigation system having a map data base, the method comprising the steps of: storing a first vehicle position; moving the vehicle from the first vehicle position; sensing an external signal while moving the vehicle; detecting a change in the external signal caused by the presence of a landmark; examining the map data base to find a most likely landmark position corresponding to the change in the external signal; and updating the current vehicle position to the most likely landmark position.
Claim 3
Dependent Claim
23 words
A method as in claim 1 wherein the step of sensing an external signal comprises receiving a GPS signal transmitted from a satellite.
Claim 4
Dependent Claim
26 words
A method as in claim 2 wherein the step of detecting a change in the external signal comprises detecting a failure to receive the GPS signal.
Claim 5
Dependent Claim
25 words
A method as in claim 3 wherein the landmark comprises a structure under which the vehicle passes such that the GPS signal is temporarily blocked.
Claim 6
Dependent Claim
20 words
A method as in claim 4 wherein the structure is taken from the group consisting of overpasses, tunnels and bridges.
Claim 7
Dependent Claim
25 words
A method as in claim 1 wherein the step of sensing an external signal comprises sensing a geomagnetic field to provide a first heading signal.
Claim 8
Dependent Claim
18 words
A method as in claim 6 wherein the landmark comprises a structure causing anomalies in the geomagnetic field.
Claim 9
Dependent Claim
22 words
A method as in claim 7 wherein the structure is taken from the group consisting of bridges, tunnels, buildings and geologic formations.
Claim 10
Dependent Claim
53 words
A method as in claim 6 wherein the step of detecting a change in the external signal comprises comparing the first heading signal to a second heading signal, the second heading signal being independent of the geomagnetic field, to detect a difference between the first and second heading signals caused by the landmark.
Claim 11
Dependent Claim
16 words
A method as in claim 9 wherein the second heading signal is generated by a gyroscope.
Claim 12
Dependent Claim
27 words
A method as in claim 9 wherein the step of comparing comprises filtering out differences between the first and second heading signals not caused by the landmark.
Claim 13
Dependent Claim
121 words
A method as in claim 11 wherein the filter comprises a digital auto-regressive moving-average filter of the form: ##EQU3## where: y(k) is a magnetic anomaly index; k is a current sample time; a l are auto-regressive coefficients; b j are moving-average coefficients; m is a number of past y(k) values included in a present value; n is a number of present and past values of a filter input which are to be averaged; and u(k) is the difference between the first heading signal and the second heading signal, u(k) being the input to the auto-regressive moving-average filter; wherein the change in the geomagnetic signal is considered to be caused by the landmark when the magnetic anomaly index exceeds a predetermined value.
Claim 14
Dependent Claim
59 words
A method as in claim 1 further comprising: measuring the distance between the first vehicle position and the current vehicle position to obtain a measured distance; calculating an actual distance between the first vehicle position and the current vehicle position from the map data base; and determining a distance calibration factor relating the measured distance to the actual distance.
Claim 15
Dependent Claim
109 words
Apparatus for determining a current vehicle position in a vehicle navigation system having a map data base, the apparatus comprising: a memory for storing a first vehicle position; a sensor for sensing an external signal while the vehicle moves; and processing means coupled to the map data base, the memory and the sensor, the processing means comprising: means for detecting a change in the external signal caused by the presence of a landmark; means for examining the map data base to find a most likely landmark position corresponding to the change in the external signal; and means for updating the current vehicle position to the most likely landmark position.
Claim 16
Dependent Claim
109 words
Apparatus for determining a current vehicle position in a vehicle navigation system having a map data base, the apparatus comprising: a memory for storing a first vehicle position; a sensor for sensing an external signal while the vehicle moves; and processing means coupled to the map data base, the memory and the sensor, the processing means comprising: means for detecting a change in the external signal caused by the presence of a landmark; means for examining the map data base to find a most likely landmark position corresponding to the change in the external signal; and means for updating the current vehicle position to the most likely landmark position.
Claim 17
Dependent Claim
24 words
The apparatus of claim 14 wherein the external signal comprises a GPS signal transmitted from a satellite, and the sensor comprises a GPS receiver.
Claim 18
Dependent Claim
24 words
The apparatus of claim 15 wherein the means for detecting a change in the external signal detects a failure to receive the GPS signal.
Claim 19
Dependent Claim
24 words
The apparatus of claim 16 wherein the landmark comprises a structure under which the vehicle passes such that the GPS signal is temporarily blocked.
Claim 20
Dependent Claim
19 words
The apparatus of claim 17 wherein the structure is taken from the group consisting of overpasses, tunnels and bridges.
Claim 21
Dependent Claim
27 words
The apparatus of claim 14 wherein the sensor comprises a geomagnetic field sensor, the geomagnetic field sensor sensing a geomagnetic field and producing a first heading signal.
Claim 22
Dependent Claim
17 words
The apparatus of claim 19 wherein the landmark comprises a structure causing anomalies in the geomagnetic field.
Claim 23
Dependent Claim
21 words
The apparatus of claim 20 wherein the structure is taken from the group consisting of bridges, tunnels, buildings and geologic formations.
Claim 24
Dependent Claim
57 words
The apparatus of claim 19 wherein the means for detecting a change in the external signal comprises means for comparing the first heading signal to a second heading signal, the second heading signal being independent of the geomagnetic field, to detect a difference between the first heading signal and the second heading signal caused by the landmark.
Claim 25
Dependent Claim
15 words
The apparatus of claim 22 wherein the second heading signal is generated by a gyroscope.
Claim 26
Dependent Claim
29 words
The apparatus of claim 22 wherein the means for comparing comprises a filter for filtering out differences between the first and second heading signals not caused by the landmark.
Claim 27
Dependent Claim
120 words
The apparatus of claim 24 wherein the filter comprises a digital auto-regressive moving-average filter of the form: ##EQU4## where: y(k) is a magnetic anomaly index; k is a current sample time; a l are auto-regressive coefficients; b j are moving-average coefficients; m is a number of past y(k) values included in a present value; n is a number of present and past values of a filter input which are to be averaged; and u(k) is the difference between the first heading signal and the second heading signal, u(k) being the input to the auto-regressive moving-average filter; wherein the change in the geomagnetic signal is considered to be caused by the landmark when the magnetic anomaly index exceeds a predetermined value.
Claim 28
Dependent Claim
71 words
The apparatus of claim 14 further comprising a distance sensor for measuring the distance between the first vehicle position and the current vehicle position to obtain a measured distance, wherein the processor means comprises means for calculating an actual distance between the first vehicle position and the current vehicle position from the map data base, and means for determining a distance calibration factor relating the measured distance to the actual distance.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-12-19 | 1998-06-20 | 1998-12-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-12-19 | 2002-06-20 | 2002-12-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-12-19 | 2006-06-20 | 2006-12-20 | $7700.00 | Window Closed / Lapsed |